RPI - CANOpen

Links

https://www.autopi.io/blog/canopen-simple-introduction-explained/

https://copperhilltech.com/cangineberry-canopen-module-for-raspberry-pi/

https://www.seeedstudio.com/CAN-BUS-FD-HAT-for-Raspberry-Pi-p-4742.html?gad=1&gclid=Cj0KCQjwk96lBhDHARIsAEKO4xYAmLdGQNoTgtlQiTcZrmM7NoMeBFUGK7oMgsC-L3k_4WfpV43_WLYaAnTaEALw_wcB

https://www.autopi.io/blog/raspberry-pi-can-bus-explained/#:~:text=The%20Raspberry%20Pi%20hardware%20does,the%20CAN%20Bus%20(Raspbian).

https://copperhilltech.com/search.php?search_query=pican3&Search=

Extenders

Various extender/repeaters or fiber media converters

Bus extender: https://www.vitalsystem.com/can/canr.php

Bridge: https://www.icpdas-usa.com/i_7532.html

Media converter (fiber): https://moxastore.express-inc.com/ICF_1170I_M_ST_p/icf-1170i-m-st.htm

Cable length verses data rate: CAN Bus

Bit Rate Bus Length

• 1 Mbit/s 30 m
• 800 kbit/s 50 m
• 500 kbit/s 100 m
• 250 kbit/s 250 m
• 125 kbit/s 500 m
• 62.5 kbit/s 1000 m

RS-232

• Bit Rate Bus Length
• 115200 bit/s 2.5 m
• 57600 bit/s 5.0 m
• 38400 bit/s 7.5 m
• 19200 bit/s 15 m
• 9600 bit/s 30 m

Config

Running a Seeed mcp2518fd based board with 2 can bus.

after boot, should see the following:

$ dmesg | grep can

[   11.115212] mcp251xfd spi0.1 can0: MCP2518FD rev0.0 (-RX_INT -PLL -MAB_NO_WARN +CRC_REG +CRC_RX +CRC_TX +ECC -HD o:40.00MHz c:40.00MHz m:20.00MHz rs:17.00MHz es:16.66MHz rf:17.00MHz ef:16.66MHz) successfully initialized.

[   11.217854] mcp251xfd spi0.0 can1: MCP2518FD rev0.0 (-RX_INT -PLL -MAB_NO_WARN +CRC_REG +CRC_RX +CRC_TX +ECC -HD o:40.00MHz c:40.00MHz m:20.00MHz rs:17.00MHz es:16.66MHz rf:17.00MHz ef:16.66MHz) successfully initialized.

Now set the interface "up":

$ sudo ip link set can0 up type can bitrate 100000

$ sudo ip link set can1 up type can bitrate 100000

Now testing the link with can0 connected to can1.

$ candump can0

$ cansend can1 111#ff

CANopen message structure

The CANopen frame contains the arbitration field (12 bits) and data fields (8 bytes)

CANopen frame sequence

The arbitration field contains an 11 bit identifier (COB-ID) which describes the message types. The cob-id defines the message priority, 0 is the highest, 0x7ff is the lowest. It also contains a 1 bit RTR (remote transmit request). This requests a response from the target device.

Arbitration Fields

NMT messages have cob-id of 0 (zero). These messages request the communication state of the node-id (data byte 2) be set to the designated state in data byte 1.

NMT message structure

Node Id is set on the device, can not be set via the CANopen protocols.